High propane recovery process and configurations

ABSTRACT

A gas processiing plant has a de-ethaniizer ( 106 ) and a rctluxed absorber ( 103 ), wherein the absorber ( 103 ) operates at higher pressure than the de-ethanizer ( 106 ), and wherein at least a portion of the absorber bottoms product ( 7 ) is expanded to provide cooling for the absorber reflux stream and/or the distillation column feed stream. Especially contemplated gas processing plants include propane and ethane recovery plants, and where the gas processing plant is an ethane recovery plant, it is contemplated that the ethane product comprises no more than 500 ppm carbon dioxide.

FIELD OF THE INVENTION

[0001] The field of the invention is recovery of a gas fraction from afeed gas, and particularly relates to propane recovery.

BACKGROUND OF THE INVENTION

[0002] Many natural and man-made gases comprise a variety of differenthydrocarbons, and numerous methods and configurations are known in theart to produce commercially relevant fractions from such gases. Amongother processes, cryogenic gas separation (see e.g., U.S. Pat. No.4,157,904 to Campbell et al., U.S. Pat. No. 4,690,702 to Paradowski etal., or U.S. Pat. No. 5,275,005 to Campbell et al.) has become apreferred method of gas separation.

[0003] In a typical gas separation process, a feed gas stream underpressure is cooled by heat exchanger and as the gas cools, liquidscondense from the cooled gas. The liquids are then expanded andfractionated in a distillation column (e.g., de-ethanizer orde-methanizer) to separate residual components such as methane, nitrogenand other volatile gases as overhead vapor from the desired C₂, C₃ andheavier components. In some configurations, uncondensed cooled feed gasis expanded to condense additional liquid, which may subsequently beemployed as C₂ and C₃ absorbing agent in an absorber. Variousimprovements on the basic concept of cryogenic gas separation have beendeveloped.

[0004] For example, Rambo et al. describe in U.S. Pat. No. 5,890,378 asystem in which (a) the absorber is refluxed, (b) in which thede-ethanizer condenser provides the reflux for both the absorber and thede-ethanizer while the cooling requirements are met using aturboexpander, and (c) in which the absorber and the de-ethanizeroperate at substantially the same pressure. Although Rambo'sconfiguration advantageously reduces capital cost for equipmentassociated with providing reflux for the absorption section and thede-ethanizer, propane recovery significantly decreases as the operatingpressure in the absorber rises, especially at a pressure above 500 psig,where separation of ethane from propane in the de-ethanizer becomesincreasingly difficult. Consequently, Rambo's system is generallylimited by the upper operating limit of the de-ethanizer pressure.Increasing of the absorber pressure while maintaining desirable propanerecovery becomes difficult, if not impossible in Rambo's processconfiguration. Moreover, operating the absorber and de-ethanizer at apressure af or below 500 psig typically necessitates higher residue gasrecompression, thereby incurring relatively high operating cost.

[0005] To circumvent at least some of the problems associated withrelatively high cost associated with residue gas recompression, Sorensendescribes in U.S. Pat. No. 5,953,935 a plant configuration in which anadditional fractionation column is included. The absorber reflux inSorensen's plant configuration is produced by compressing, cooling, andJoule Thomson expansion of a slipstream of feed gas. Although Sorensen'sconfiguration generally provides an improved propane recovery withsubstantially no increase in plant residue compression horsepower,propane recovery significantly decreases as the operating pressure inthe absorber rises, especially at a pressure above about 500 psig.Furthermore, ethane recovery using such known systems designed forpropane recovery is normally limited to about 20% recovery.

[0006] In order to improve ethane recovery with a low CO₂ content in theethane product, Campbell describes in U.S. Pat. No. 6,182,469 a towerreboiling scheme in which one or more tower liquid distillation streamsfrom a point higher in the absorber are employed for stripping ofundesirable components (e.g., carbon dioxide in a demethanizer).Campbell's scheme typically requires over-stripping of the ethaneproduct, and CO₂ removal is generally limited to about 6%. Moreover,additional CO₂ removal using Campbell's process will significantlyreduce ethane recovery, and increase power consumption. Furthermore, andespecially where the ethane product is used for chemical production, theproduct in Campbell's configuration typically requires further treatmentto remove CO₂ to or below a level of 500 ppmv, which often requiressubstantial capital and operating expenditure.

[0007] Although there are various configurations and processes forimproved propane and ethane recovery known in the art, all or almost allof them, suffer from one or more disadvantage. Therefore, there is stilla need to provide improved methods and compositions for high propanerecovery processes and configurations.

SUMMARY OF THE INVENTION

[0008] The present invention is directed to methods and configurationsof a gas plant comprising a refluxed absorber producing a bottomsproduct stream and receiving a feedstock and an absorber reflux stream.A distillation column is fluidly coupled to the absorber, receives adistillation column feed stream and operates at a pressure that is atleast 100 psi lower than the operating pressure of the absorber.

[0009] In one aspect of the inventive subject matter, the distillationcolumn comprises a de-ethanizer column, the feedstock has a pressure ofbetween l000 psig and 2000 psig, and is expanded in a turbine expander.The bottoms product of the absorber is expanded in a range of 100-250psi, thereby cooling the product to a temperature between −95° F. to−125° F. It is also contemplated that the cooled and expanded bottomsproduct stream is then fed as the distillation column feed stream intothe distillation column, and it is still further contemplated that theexpanded bottoms product stream may further provide cooling for adistillation column reflux stream. In a particularly contemplated aspectthe distillation column produces an overhead stream that is compressed,cooled, and fed into the absorber as the absorber reflux stream.

[0010] In another aspect of the inventive subject matter, thedistillation column comprises a de-ethanizer column, the feedstock has apressure of between 550 psig and 800 psig, and is not expanded in aturbine expander. The bottoms product of the absorber is expanded in arange of 100-250 psi, thereby cooling the product to a temperaturebetween −50° F. to −70° F. It is also contemplated that the cooled andexpanded bottoms product stream is then fed as the distillation columnfeed stream into the distillation column, and that at least a portion ofthe feedstock is fed into a lower section of the distillation column. Ina further contemplated aspect, an external refrigeration is coupled tothe distillation column and feed exchanger.

[0011] In a still further aspect of the inventive subject matter, thedistillation column comprises a demethanlzer, the feedstock is at apressure of between 1000 psig and 2000 psig, and is expanded in aturboexpander. It is also contemplated that in such configurations theabsorber bottoms product is expanded in a range of 100-250 psi, therebycooling the bottoms product stream to a temperature of between −95° F.to −125° F. It is further contemplated that the expanded bottoms productis fed as the distillation column feed stream into the distillationcolumn, wherein the distillation column produces a distillation columnoverhead stream that is compressed, cooled, and fed into the absorber asthe absorber reflux stream, and that the distillation column produces adistillation column product stream that comprises no more than 500 ppmcarbon dioxide. In particularly contemplated aspects, the feedstock issplit into a first portion and a second portion, and wherein an externalrefrigeration cools at least part of the first portion, and wherein atleast one side reboiler located in the upper section of the distillationcolumn (i.e. is fluidly coupled to the demethanizer between a top trayand a position eight trays below the top tray), provides reboiling ofthe distillation column, provides heat duty for stripping of CO₂ fromthe demethanizer product stream, and further provides cooling of thefirst portion of the feedstock.

[0012] Various objects, features, aspects and advantages of the presentinvention will become more apparent from the following detaileddescription of preferred embodiments of the invention, along with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING

[0013]FIG. 1 is a prior art schematic of an exemplary gas processingplant for propane recovery.

[0014]FIG. 2 is a schematic of an exemplary configuration for gasprocessing plant for propane recovery with a turboexpander, a feed gaspressure of about 1300 psig, and a de-ethanizer as distillation column.

[0015]FIG. 2A is a graph depicting a heat composite curve for heatexchanger 100 in a plant configuration according to FIG. 2.

[0016]FIG. 3 is a prior art schematic of another exemplary gasprocessing plant for ethane recovery.

[0017]FIG. 4 is a schematic of a further exemplary configuration for agas processing plant for ethane recovery with a turboexpander, a feedgas pressure of about 1300 psig, and a demethanizer as distillationcolumn.

[0018]FIG. 4A is a graph depicting a heat composite curve for heatexchanger 100 in a plant configuration according to FIG. 4.

[0019]FIG. 4B is a graph depicting a heat composite curve for a sideheat exchanger 116 in a plant configuration according to FIG. 4.

[0020]FIG. 5 is a schematic of yet another exemplary configuration for agas processing plant without turboexpander, a feed gas pressure of about750 psig, and a de-ethanizer as distillation column.

[0021]FIG. 6 is a schematic of an exemplary configuration for a gasprocessing plant in which the refluxed absorber and the distillationcolumn are configured in a single tower.

DETAILED DESCRIPTION

[0022] The inventors discovered that high propane recovery (i.e., atleast 95%) from a feed gas with relatively high (e.g., between about1000 psig to 2000 psig) to relatively low (e.g., between about 550 psigto 800 psig) pressure can be realized by operating an absorber in a gasprocessing plant at a significantly higher pressure than a distillationcolumn (e.g., a de-ethanizer), and in which the absorber bottoms productis expanded to provide cooling for the absorber reflux stream and/or thedistillation column feed. The inventors have further discovered thatsuch configurations may also be employed to significantly increaseethane recovery from feed gas with relatively high pressure, and tosignificantly remove CO₂.

[0023] More particularly, the inventors contemplate a gas processingplant that comprises a refluxed absorber operating at a first pressure,that produces a bottoms product stream and that receives a feedstock andan absorber reflux stream. Contemplated configurations further include adistillation column that is fluidly coupled to the absorber thatreceives a distillation column feed stream and that is operated at asecond pressure, which is at least 100 psi lower than the operatingpressure of the absorber, wherein at least a portion of the bottomsproduct stream is expanded and provides cooling for the absorber refluxstream and/or the distillation column feed stream.

[0024] Prior art FIG. 1 depicts a known configuration for a propanerecovery plant in which a feed gas stream 1 at a pressure of about 1300psig is cooled in a heat exchanger 100, separated into a gaseous and aliquid phase, and the gaseous phase is then expanded in a turboexpander102 and fed into the absorber 103, which operates at a pressure of about450 psig. The liquid phase (if present) is Joule-Thomson (JT) expanded,and directly fed into a lower portion of the absorber. The bottomsproduct of the absorber is pumped via pump 104 through heat exchanger100, and the heated bottoms product is subsequently fed into thede-ethanizer.

[0025] The absorber 103 is refluxed using cooled de-ethanizer overheadstream 14, wherein the cooling of the reflux is provided by the overheadvapor from the absorber, which is further heated in heat exchanger 100prior to recompression in recompressor 112 and subsequent residue gascompressor 113. Absorber 103 further provides reflux stream 17 that isfed into the de-ethanizer via pump 108. Liquid product stream 12 leavesthe de-ethanizer with a propane recovery typically above 95%.

[0026] In contrast, a particularly preferred configuration of a gasprocessing plant for propane recovery as depicted in FIG. 2 has arefluxed absorber 103 that is operated at a pressure of about 590 psigand a de-ethanizer 106 that is operated at a pressure of about 410 psig,while the feed gas stream 1 has a pressure of about 1300 psig. The feedgas stream 1 is cooled in heat exchanger 100 and separated in aseparator 101 in a liquid portion 5 and a gaseous portion 4. The liquidportion 5 (if present) is fed into the absorber 103, while the gaseousportion 4 is expanded in a turboexpander 102 to the level of theoperating pressure of the absorber. Expanded gaseous portion 6 is thenfed into a lower section of the absorber 103. The absorber 103 receivesa reflux stream 19, which is provided by the overhead stream 13 of thede-ethanizer 106. The overhead stream 13 is cooled in a heat exchanger105, and separated in a separator 107 in a gaseous phase 15 and a liquidphase 16. Liquid phase 16 is pumped back to the de-ethanizer asde-ethanizer reflux via pump 108, while gaseous phase 15 is compressedin compressor 111 and cooled in the heat exchanger 100 before enteringthe absorber as reflux stream 19.

[0027] The absorber bottoms stream 7 is expanded in JT valve 104,thereby lowering the pressure in an amount of about 180 psi andsignificantly cooling the absorber bottoms stream. The cooled absorberbottoms stream 8 is then employed as a coolant in the heat exchangers100 and 105 before entering de-ethanizer 106 as de-ethanizer feed stream11. Absorber overhead stream 9 is heated in the heat exchanger 100 andrecompressed in recompressor 112 (which is operationally coupled to theturboexpander). Recompressed overhead stream 21 is farther compressed inresidue gas compressor 113 and fed into a residue gas pipeline. Thede-ethanizer bottoms stream 12 provides liquid product at a propanerecovery of at least 99%.

[0028] With respect to the feed gas streams it is contemplated thatnumerous natural and manmade feed gas streams are suitable for use inconjunction with the teachings presented herein, and especiallypreferred feed gas streams include natural gases, refinery gases, andsynthetic gas streams from hydrocarbon materials such as naphtha, coal,oil, lignite, etc. Consequently, the pressure of contemplated feed gasstreams may vary considerably. However, it is generally preferred thatappropriate feed gas pressures for plant configurations according toFIG. 2 will generally be in the range between 1000 psig and 2000 psig,and that at least a portion of the feedstock is expanded in aturboexpander to provide cooling and/or power for the residue gasrecompression.

[0029] Depending on the pressure of the feed gas and the amount of feedgas expansion in the turboexpander, the operating pressure for theabsorber may vary in the range from between 500 psig to 800 psig, morepreferably between 500 psig and 750 psig and most preferably between 550psig and 700 psig. Thus, it should be especially appreciated that thebottoms product stream has leave the absorber at a considerablepressure, and that cooling can be provided from expanding the bottomsproduct stream to a lower pressure. In a particularly contemplatedaspect, expansion of the bottoms product stream reduces the bottomsproduct stream pressure in a range of about 100 psi to about 250 psi,and more preferably in a range of about 150 psi to 200 psi. Thus, it iscontemplated that the absorber is operated at a pressure that is atleast 100 psi higher than the pressure of the distillation column,however, alternative pressure differences are also contemplated andinclude absorber pressure differences of less than 100 psi (e.g.,between 50 psi and 99 psi, and even less), and particularly includeabsorber pressure differences of more than 100 psi (e.g., between 101psi and 150 psi, more preferably between 151 psi and 250 psi, and evenhigher).

[0030] Consequently, it should be appreciated that the temperature ofthe expanded bottoms product stream will be in a range of about −95° F.to −125° F. Therefore, it is contemplated that the expanded bottomsproduct stream may further provide cooling for various streams withinthe gas processing plant, and it is especially contemplated that theexpanded bottoms product stream further cools a distillation columnoverhead stream, and absorber reflux. It is still further contemplatedthat the expanded bottoms product stream may be fed into thedistillation column at various positions, however, it is particularlypreferred that the expanded bottoms product stream is fed into thedistillation column at a position below the feed point of the reflux(e.g., at least three trays below the upmost tray in the distillationcolumn)

[0031] With respect to the distillation column it should be especiallyappreciated that the distillation column produces a distillation columnoverhead stream that is compressed, cooled, and fed into the absorber asthe absorber reflux stream, thereby providing a particularly lean stream(stream 13 containing 64 mol % methane and 33 mol % ethane) that maybeemployed to recover the propane and heavier components from the expandedfeed gas streams. Thus contemplated configurations according to FIG. 2receive a feedstock that comprises propane, and provide a distillationcolumn product stream that comprises at least 95% of the propane in thefeedstock.

[0032] In another particularly preferred aspect of the inventive subjectmatter, a gas processing plant as depicted in FIG. 5 has a refluxedabsorber 103 that is operated at a pressure of about 720 psig and ade-ethanizer 106 that is operated at a pressure of about 500 psig, whilethe feed gas stream 1 has a pressure of about 760 psig. The feed gasstream 1 is separated in separator 101 in a liquid portion 5 and agaseous portion 2. The liquid portion is JT expanded in JT valve 115 anddirectly fed into the de-ethanizer column 106. The gaseous portion 2 iscooled in a heat exchanger 100 and the cooled gaseous portion 6 is thenfed into absorber 103 without expansion in a turboexpander. The absorber103 receives a reflux stream 19, which is provided by the overheadstream 13 from the reflux drum 102 of the de-ethanizer 106. Thede-ethanizer overhead stream 13, coupled with an external refrigerationstream 109, and absorber overhead vapor stream 9 are used to cool thefeed stream 2 in exchanger 100. The de-ethanizer overhead stream 13 isheated to ambient temperature in exchanger 100 by the feed stream inexchanger 100, and is then compressed in a compressor to stream 18. Thecompressor discharge stream 18 is cooled in an air cooled exchanger 114and then further chilled in heat exchanger 105 with absorber bottomsstream 8 before entering the absorber as reflux stream 19.

[0033] The absorber bottoms stream 7 is expanded in JT valve 104,thereby lowering the pressure in an amount of about 210 psi andsignificantly cooling the absorber bottoms stream from −47° F. to −61°F. The expanded and cooled absorber bottoms stream 8 is then employed asa coolant in the heat exchanger 105 before entering de-ethanizer 106 asde-ethanizer feed stream 11. Absorber overhead stream 9 is heated in theheat exchanger 100 and fed into the residue gas pipeline withoutrecompression. The de-ethanizer bottoms stream 12 provides liquidproduct at a propane recovery of at least 95%.

[0034] With respect to the type and chemical composition of the feed gasthe same consideration as described above apply. However, in plantconfigurations according to FIG. 5, the feed gas has a pressure ofbetween about 550 psig and about 800 psig, and most preferably betweenabout 600 psig and about 750 psig. It should be particularly appreciatedthat operation of the absorber at a higher pressure allows that the feedgas is fed into the absorber without passing through a turboexpander.Consequently, the pressure in the absorber bottoms product (which ispreferably rich in methane) may advantageously be employed forrefrigeration of various streams in the plant.

[0035] Thus, it is contemplated that the absorber bottoms product streamis expanded to reduce the bottoms product stream pressure in a range ofabout 50 psi to about 350 psi, and more preferably in a range of about10 psi to about 250 psi. Consequently, it is contemplated that thebottoms product stream will have a temperature between −30° F. to −80°F., and more typically between about between −50° F. to −70° F. Whilenot limiting to the inventive subject matter, it is generallycontemplated that the expanded bottoms product stream is fed as thedistillation column feed stream into the distillation column below thetop of the distillation column, and it is preferred that the expandedbottoms product stream is fed into the distillation column at a positionthat is at least three trays below an upmost tray in the distillationcolumn. With respect to the liquid portion of the feed gas, it isgenerally preferred that at least a portion of the feed gas is fed intoa lower section of the distillation column.

[0036] It should further be appreciated that during propane recovery,the absorber bottoms after it is used to chill the absorber overheadreflux, is farther utilized (if residual refrigeration is available) tocool the de-ethanizer overhead vapor providing reflux to thede-ethanizer. The heated absorber bottoms product stream at about −30°F. to about −50° F. is fed to a feed tray located at least 3 trays fromthe utmost top of the de-ethanizer. This arrangement improves theoverall fractionation performance of the de-ethanizer by providingreflux and additional rectification utilizing the refrigeration contentby the JT of the absorber bottoms. The de-ethanizer operates at anoverhead temperature between −20 to −55° F.

[0037] With respect to the de-ethanizer it should be especiallyappreciated that the de-ethanizer produces an overhead stream that iscooled, and fed into the absorber as the absorber reflux stream, therebyproviding a particularly lean stream (stream 13 containing 75 mol %methane and 25 mol % ethane) that may be employed to recover the propaneand heavier components from the feed gas stream. Thus, contemplatedconfigurations according to FIG. 5 receive a feedstock that comprisespropane, and provide a distillation column product stream that comprisesat least 95% of the propane in the feedstock.

[0038] In a still further contemplated aspect of the inventive subjectmatter, contemplated configurations may further be employed in a gasprocessing plant for ethane recovery from a feed gas. FIG. 3 depicts aprior art configuration in which a feed gas stream 1 at a pressure ofabout 1300 psig is cooled and separated into a gaseous portion 4 andliquid portion 5. The gaseous portion is split in two streams, and thefirst stream cooled and JT expanded, while the second stream is passedthrough a turboexpander. Both streams are then fed into differentlocations in the demethanizer. The demethanizer operates at about 430psig. The demethanizer overhead provides cooling for the first streamand is recompressed by the turboexpander and further compressed by theresidue gas compressor before leaving the plant as residue gas. Typicalethane recovery is about 80%, and the CO₂ content in the ethane productis about 2 to 6%.

[0039] In contrast, an ethane recovery plant configurations according tothe inventive subject matter as shown in FIG. 4 has a refluxed absorber163 that is operated at a pressure of about 590 psig and a de-ethanizer106 that is operated at a pressure of about 450 psig, while the feed gasstream 1 has a pressure of about 1300 psig. The feed gas stream 1 issplit into a first portion 2 a and a second portion 2 b. The firstportion 2 a is cooled in heat exchanger 100 and the second portion 2 bis cooled in heat exchanger 116. The respective cooled fed gas streams 3a and 3 b are combined and separated in a separator 101 in a liquidportion 5 and a gaseous portion 4. The liquid portion 5 (if present) isfed into the absorber 103 after JT expansion in JT valve 115, while thegaseous portion 4 is expanded in a turboexpander 102 to the level of theoperating pressure of the absorber 103. Expanded gaseous portion 6 isthen fed into a lower portion of the absorber 103′. The absorber 103receives a reflux stream 19, which is provided by the demethanizeroverhead stream 13 of the demethanizer 106. The overhead stream 13 isseparated in a separator 107 in a gaseous phase 15 and a liquid phase16. Liquid phase 16 is pumped back to the demethanizer as demethanizerreflux via pump 108, while gaseous phase 15 is compressed in compressor111 and cooled in the heat exchanger 100 before entering the absorber asreflux stream 19.

[0040] The absorber bottoms stream 7 is expanded in JT valve 104,thereby lowering the pressure in an amount of about 110 psi andsignificantly cooling the absorber bottoms stream. The cooled absorberbottoms stream 8 is then employed as a coolant in the heat exchanger 100before entering demethanizer 106 as demethanizer feed stream 11.Absorber overhead stream 9 is heated in the heat exchanger 100 andrecompressed in recompressor 112 (which is operationally coupled to theturboexpander). Recompressed overhead stream 21 is further compressed ina residue gas compressor 113 and fed into a residue gas pipeline. Thedemethanizer bottoms stream 12 provides liquid product at an ethanerecovery of at least 69.0% and a CO2 content of no more than 500 ppm.Two side reboilers, located in the top section of the demethanizer,withdraw distillation liquids stream 109A and 109B. These streams arecoupled to the distillation column and provide heat duties for the bulkremoval of CO₂ from the liquid product, and further provide cooling ofthe first portion of the feedstock by stream 109A and 109B. The residualCO₂ is removed in the bottom reboiler 110.

[0041] Suitable feed gases are contemplated to have a pressure ofbetween 100 psig and 2000 psig. Consequently, it is preferred that atleast a portion of the feed gas is expanded in a turboexpander. Furthercooling is provided by expanding the bottoms product stream in a rangeof 100-250 psi. Consequently, it is contemplated that the expandedbottoms product stream has a temperature between −95° F. to −125° F.

[0042] With respect to the de-methanizer it should be especiallyappreciated that the demethanizer column produces an overhead streamthat is compressed, cooled, and fed into the absorber as the absorberreflux stream, thereby providing a particularly lean stream (stream 13containing over 90 mol % methane) that may be employed to recover theethane and heavier components from the expanded feed gas streams. Thuscontemplated configurations according to FIG. 4 receive a feedstock thatcomprises ethane and propane, and provide a distillation column productstream that comprises at least 60% of the ethane and 95% of the propanein the feedstock

[0043] It should be particularly recognized that contemplatedconfigurations according to FIG. 4 can be used for a recovery of up to75% ethane without appreciable increase in capital and operating costsfor ethane recovery when the system can be used for high propanerecovery of FIG. 2. In an especially contemplated configuration, thefeed tray location to the demethanizer is routed to the top of thedemethanizer, and the overhead reflux condenser 105 in FIG. 2 may beconverted for use as a side reboiler 116 of the demethanizer in FIG. 4.Additional side-reboilers, and external refrigeration may be used toimprove the overall energy efficiency. The demethanizer overhead refluxsystem is bypassed in this operation and the demethanizer now operatesas a reboiled stripper (as compared to a fractionator during propanerecovery). The basic equipment design and arrangement in the upstreamsystem is maintained as in FIG. 2, but with a lower operatingtemperature. The absorber overhead operates then at a lower temperatureof about −100° F. to about −130° F., and the feed temperature to thedemethanizer is at a lower temperature of about −100° F. to about −120°F.

[0044] It should further be appreciated that the previously knownrecovery plants designed for propane recovery can recover ethane in arange of 20% to 40%. In contrast, configurations according to theinventive subject matter, with minor changes in operation and processparameters, can be economically used for ethane recovery up to 75%.Moreover, the ethane produced in previously known recovery plantsdesigned for ethane recovery usually contains 26% CO₂. In contrast,configurations according to the inventive subject matter will allowethane recovery in which the CO₂ is present in the ethane in an amountof less than 500 ppm, and more typically less than 350 ppm.

[0045] With respect to all components of contemplated configurations(e.g., heat exchangers, pumps, valves, compressors, expanders, refluxedabsorbers, de-ethanizers, etc.) it should be appreciated that all knownand commercially available components are suitable for use inconjunction with the teachings presented herein. It is farther generallycontemplated that configurations according to the inventive subjectmatter may find wide applicability in gas plant applications where highpropane recovery is desirable, and feed gas is available at pressuregreater than 550 psig. Moreover, such configurations may advantageouslyreduce equipment and operating costs, especially where turboexpandertechnology would necessitate feed gas and/or residue gas compression.For gas plant applications where energy cost is relatively high andpropane value compared to fuel value is marginal, it is contemplatedthat preferred design configurations greatly reduce the overall energycompression costs by operating the absorber between 600 to 750 psigwhile maintaining the propane recovery between 85% to 95%. Furthermore,it should be appreciated that by combining the reflux absorber andde-ethanizer in a single column as shown in FIG. 6, the overall plotspace requirement maybe reduced, which may result in substantial costsavings in modular and platform design.

EXAMPLES

[0046] Operations of gas processing plants according to FIGS. 1, 2, 3,4, and 5 were computer simulated using process simulator HYSYS, andTables 1, 2, 3, 4, and 5 below summarize exemplary component flow,pressures and temperatures in the configurations as shown in FIGS. 1-5,respectively.

[0047] Furthermore, calculations were performed to project the heatcomposite curve for the heat exchanger 100 in plant configurationaccording to FIG. 2, the heat exchanger 100 in plant configurationaccording to FIG. 4, and the side heat exchanger 116 in plantconfiguration according to FIG. 4, and the results are depicted in FIGS.2A, 4A, and 4B, respectively. The energy efficiencies of theseinventions are very high that are demonstrated by the relatively closetemperature approaches of these composite curves.

[0048] Thus, specific embodiments and applications for high propanerecovery processes and configurations have been disclosed. It should beapparent, however, to those skilled in the art that many moremodifications besides those already described are possible withoutdeparting from the inventive concepts herein. The inventive subjectmatter, therefore, is not to be restricted except in the spirit of theappended claims. Moreover, in interpreting both the specification andthe claims, all terms should be interpreted in the broadest possiblemanner consistent with the context. In particular, the terms “comprises”and “comprising” should be interpreted as referring to elements,components, or steps in a non-exclusive manner, indicating that thereferenced elements, components, or steps may be present, or utilized,or combined with other elements, components, or steps that are notexpressly referenced.

What is claimed is:
 1. A gas processing plant comprising: a refluxedabsorber operating at a first pressure, producing a bottoms productstream and receiving a feedstock and an absorber reflux stream; adistillation column fluidly coupled to the absorber, receiving adistillation column feed stream and operating at a second pressure thatis at least 100 psi lower than the first pressure; and wherein at leasta portion of the bottoms product stream is expanded and provides coolingfor at least one of the absorber reflux stream and the distillationcolumn feed stream.
 2. The gas processing plant of claim 1 wherein thedistillation column comprises a de-ethanizer column.
 3. The gasprocessing plant of claim 2 wherein the feedstock is at a pressure ofbetween 1000 psig and 2000 psig.
 4. The gas processing plant of claim 3wherein at least a portion of the feedstock is expanded in aturboexpander.
 5. The gas processing plant of claim 3 wherein thebottoms product stream has a pressure and wherein expanding the bottomsproduct stream reduces the bottoms product stream pressure in a range of100-250 psi.
 6. The gas processing plant of claim 3 wherein the expandedbottoms product stream has a temperature between −95° F. to −125° F. 7.The gas processing plant of claim 3 wherein the expanded absorberbottoms product stream is fed as the distillation column feed streaminto the distillation column at a position that is at least three traysbelow an upmost tray of the distillation column.
 8. The gas processingplant of claim 3 wherein the expanded bottoms product stream furtherprovides cooling for a distillation column overhead stream.
 9. The gasprocessing plant of claim 3 wherein the distillation column produces adistillation column overhead stream that is compressed, cooled, and fedinto the absorber as the absorber reflux stream.
 10. The gas processingplant of claim 3 wherein the feedstock comprises propane, and whereinthe distillation column produces a distillation column product streamthat comprises at least 95% of the propane in the feedstock.
 11. The gasprocessing plant of claim 2 wherein the feedstock is at a pressure ofbetween 550 psig and 800 psig.
 12. The gas processing plant of claim 11wherein the feedstock is fed into the absorber without passing through aturboexpander.
 13. The gas processing plant of claim 11 wherein thebottoms product stream has a pressure and wherein expanding the bottomsproduct stream reduces the bottoms product stream pressure in a range of100-250 psi.
 14. The gas processing plant of claim 11 wherein thebottoms product stream has a temperature between −50° F. to −70° F. 15.The gas processing plant of claim 11 wherein the expanded bottomsproduct stream is fed as the distillation column feed stream into thedistillation column at a position that is at least three trays below anupmost tray in the distillation column.
 16. The gas processing plant ofclaim 11 wherein at least a portion of the feedstock is fed into a lowersection of the distillation column.
 17. The gas processing plant ofclaim 11 further comprising an external refrigeration coupled to thedistillation column.
 18. The gas processing plant of claim 1 wherein thedistillation column comprises a demethanizer.
 19. The method of claim 18wherein the feedstock is at a pressure of between 1000 psig and 2000psig.
 20. The gas processing plant of claim 18 wherein at least aportion of the feedstock is expanded in a turboexpander.
 21. The gasprocessing plant of claim 18 wherein the bottoms product stream has apressure and wherein expanding the bottoms product stream reduces thebottoms product stream pressure in a range of 100-250 psi.
 22. The gasprocessing plant of claim 18 wherein the expanded bottoms product streamhas a temperature between −95° F. to −125° F.
 23. The gas processingplant of claim 18 wherein the expanded bottoms product stream is fed asthe distillation column feed stream into the distillation column. 24.The gas processing plant of claim 18 wherein the distillation columnproduces a methane rich distillation column overhead stream that iscompressed, cooled, and fed into the absorber as the absorber refluxstream.
 25. The gas processing plant of claim 18 wherein thedistillation column produces a distillation column product stream thatcomprises no more than 500 ppm carbon dioxide.
 26. The gas processingplant of claim 18 wherein the feedstock is split into a first portionand a second portion, and wherein an external refrigeration cools atleast part of the first portion.
 27. The gas processing plant of claim26 further comprising at least one side reboiler coupled to thedistillation column, wherein the at least one side reboiler is fluidlycoupled to the demethanizer between a top tray and a position eighttrays below the top tray, provides heat duty for stripping CO₂ from ademethanizer product stream, provides reboiling of the distillationcolumn, and further provides cooling of the first portion of thefeedstock.
 28. The gas processing plant of claim 1, wherein the absorberand the distillation column are configured into a single towerconfiguration.